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Monday, April 13, 2015

What can you do to reduce antimicrobial resistance?

Do you consider antimicrobial resistance when treating companion animals with antimicrobials? A bearded dragon has a topical antimicrobial applied to a nasal fistula.

How
much thought do you give to the problem of antimicrobial resistance when prescribing
(or taking) antimicrobials?

The
American College of Veterinary Internal Medicine (ACVIM) has released the “ACVIM
consensus statement on therapeutic antimicrobial use in animals and
antimicrobial resistance” and it’s a worthy read.

The
statement highlights the dangers of willy-nilly antimicrobial use but also
points to areas where evidence is lacking. While many expert panels blame the
veterinary use of antimicrobials for the development of antimicrobial
resistance, the committee holds that “antimicrobial use in a single animal
species (or humans) is the main force behind development of AMR in bacteria
affecting that species” but adds that “transmission of resistant bacteria from
animals to humans is an important concern, albeit one that is inadequately
understood.”(p488).

Phil reckons Love is the Best Medicine - but he's needed more than love to deal with previous dental infections. Antimicrobials have their place but need to be used carefully. And the underlying cause (in Phil's case, some teeth that needed to be removed) must be addressed.

As
the paper states – ANY use of antimicrobials – prudent or not – exposes bacterial
pathogens and normal flora to a drug which imposes selection pressure for
resistance. Bacterial infections usually occur in the context of an inciting or
underlying cause, so attending to the underlying cause – rather than simply
changing antimicrobials or dishing out more – is important.

It’s
a paper that anyone who uses antimicrobials should read. For me, the following
points were most helpful:

Antimicrobial
resistant organisms are not necessarily more virulent. Infection which such
organisms can lead to poor clinical outcomes (including death) due to factors
not related to virulence, for example, delayed diagnosis. Rapid laboratory
identification of these organisms is therefore critical.

Prevention
of disease in the first place – through good husbandry, vaccination, excellent
care and attention to sterility - is more important than simply avoiding using
antimicrobials. And indeed, the jury is out about whether prevention of prophylactic
use of antibiotics will actually reduce resistance.

Over
the counter supply of antimicrobials online and from pet and feed supply stores
is likely to increase resistance and should be discouraged.

There
is still very little evidence around the length of an antimicrobial course.
There has been a trend to argue for longer treatment courses, but according to
the statement a shorter treatment course means that normal flora or commensal bacteria
have reduced exposure to antimicrobial drugs (there’s also likely to be better
client compliance, reduced expense, reduced inconvenience to the client and
animal, and reduced risk of adverse drug effects). There is no minimal duration
of an antimicrobial drug dose to prevent resistance. According to the paper, “antimicrobials
should never be continued once there is clinical and microbiological evidence
that an infection has been eliminated or once an alternate diagnosis has been
made” (p494).

There
is no definitive distinction between “narrow-spectrum” and “broad- spectrum”
drugs and the concept may be misleading. For example, some supposedly narrow-spectrum
agents have a huge impact on commensal flora. So these terms are avoided by the
committee.

Vets
should encourage clients to dispose of leftover antimicrobials in the practice,
as this reduces the likelihood that they will be used at the owner’s discretion
at home.

Meanwhile
if you are interested in pharmacology, the Centre for Veterinary Education is
hosting a two day symposium with some of the best pharmacology brains in the
world. You’ll need to be able to attend this Thursday and Friday. View the
program here. You do not need to be a pharmacologist to go - in fact this is very clinically focused. I went to the last one and it was accessible and extremely practical.

Veterinary Ethics: Navigating Tough Cases

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